It is interesting that the five colors did not get an equal number of these spells. Is blue/black the 'Spell Mastery color pair'?
Guideon's Phalanx should win the game with enough creatures on the board, and outside of Standard reads like a junk rare as a seven-drop instant.
Kytheon's Tactics is a sorcery, and so you cannot use it as an instant-speed battle trick. Limited card.
Swift Reckoning: nice! comes out one drop lower than a similar card from M15, Devouring Light.
Talent of the Telepath: Never mind your opponent, in a Standard format with so many good blue instants and sorceries, I would target myself in a deck full of card draw. I like it a lot for Standard constructed.
Psychic Rebuttal: an unconditional counter spell is always good even if its only good against red and black decks.
Calculated Dismissal: Limited.
Send to Sleep: I want this in Modern for my Tamiyo builds. Two mana for two creatures tapped looks like a good deal.
Dark Dabbling: the key here is that this card is an instant, and that means you can use it to counter a board wipe if you are in spell mastery territory. Me likes it.
Dark Petition: nice junk rare. 5-drop tutoring is Standard-only yet it is a fun effect. You can do a lot with three additional mana. It's a free Dark Ritual if you are in spell mastery territory.
Necromantic Summons: a five-drop reanimator is great for Standard constructed. The additional counters are not that useful because you will want to reanimate something that is already really big without the counters.
Unholy Hunger: Limited.
Exquisite Firecraft: reads like a strong card if you are in spell mastery territory. Uncounterable (not a word outside of Magic) hit for four is nothing to laugh at.
Fiery Impulse: Limited. If it read 'creature or player' it would be a way to play a Lightning Bolt in Standard.
Ravaging Blaze: Now we are talking, if you are in spell mastery territory you can hit your opponent. It takes two red mana... still good.
Gather the Pack: as a two-drop this card is very good, except that dumping cards into the graveyard is a fringe effect in mono-green. This card should be great with the black/green elves in this set.
Nissa's Pilgrimage: Nissa is in the name, and that is quite the hint, but as a three-drop it may not help with a Nissa flip... Limited?